1. Field of the Invention
The invention relates generally to a method for deriving color images from solid state image sensors wherein the blue primary color signal is enhanced. The invention particularly relates to color film scanners and cameras employing charge-coupled imaging devices.
2. Description of the Prior Art
The use of solid state image sensors, i.e. photodiodes arranged in lines or matrices, or corresponding charge-couple arrangements, for purposes of color television has so far failed because the sensitivity of these sensors is low in the blue spectral range. Therefore, color television cameras equipped with these sensors could, so far, only be used for experimental purposes with very high illumination intensities.
For the purpose of avoiding this disadvantage, it has already been proposed in German Patent Application No. P 2 644 574 to insert an image amplifier in the blue channel of a television camera which is equipped with solid state image sensors. However, this amplifier requires an additional high voltage supply on the one hand, and, on the other hand, a more expensive optical coupling in such a color television camera.
From the book by Sequin and Tompsett, "Charge Transfer Devices", Academic Press Inc., New York, 1975, especially page 185, the combination of adjacent light-sensitive elements for the purpose of improving the signal-to-noise ratio for applications with low illumination intensities is already known, but it is obtained at the expense of a deterioration of the resolution. However, this reference does not cite an application for color television. Apart from an increase in the size of the elements, there is also no indication given of the manner in which the light-sensitive elements should be combined.
It is intended that one embodiment of the present invention be considered as an improvement which can be used in connection with a color film scanner of the type described in German patent application No. P 2 632 378.